after the racket drop there is a hitch where the motion comes to a complete stop, then you just arm the racket upwards.... will never be consistent no matter how much knee bend you add, because everything up to the point of racket drop is wasted.

try to serve with only thumb, index/middle fingers on the racket, you will see it's impossible to swing with a hitch, you will have to have a continuous motion and use the centrifugal force to swing the racket up.

when the racket moves on centrifugal force, the rules of physics works FOR you and the path will be consistent. right now they are working AGAINST you.

Your entire motion is flawed.
Notice your narrow stance, and then your front foot steps forwards.
Notice your high hand at trophy.
Notice you never stop, set, and go.
Hard to get a consistent serve if you've only been playing for two years.
Watch vids of pro serving. I'd suggest JuanCarlosFerrero or LeytonHewitt.

You're a strong, athletic guy.
LOWER your arm, or keep it low, at trophy position. So you can swing upwards at the ball. A low hand, like every single male tennis pro in the world.
Change your prep stance. It's too narrow and you have no balance, and your can't move your weight forwards CONSISTENTLY. Every pro starts with a wider stance except maybe Roddick and very few others.
Stop, set, then explode.
You have the body to hit 130mph serves, with some consistency.
But not with your constantly changing technique.

I'm not an expert and others have pointed out a lot of flaws. The one overriding thing to me is there is no fluidity to your motion. Until you have that, you will never have a consistent *anything*. Start by drastically cutting down the height of that toss and then start practicing your new "motion" whenever you can. Doesn't matter if you're actually playing tennis, just start to practice the same full motion, over and over. Be sure to continually video tape yourself at the court so you know you're doing the right things.

You need a "second serve" - a serve with spin that (1) cause the ball to dip so that it passes over the net by a good amount but still stays goes into the service box and (2) although not that fast, keeps your opponent from crushing returns.

For someone starting out, I would suggest a topspin-slice serve. It sounds complicated, but all you are doing is tossing slightly to your right (if you're a righty), let the ball drop slightly below your peak swing height, and swing so your racquet goes up and along the back of the ball to put spin on the ball.

Some keys to consider- (1) you want to brush the side/back of the ball. If hit the ball too flat, you get no spin, and no dip. The reason you hear about knee bend/ swinging up at the ball is to get more upwards force (i.e., topspin on the ball) to get a higher service percentage. You will feel like you are going to frame the ball - don't worry, that is correct. Strive for a swishing brushing sound at contact and not a "pop"

2) the movement focus is up and into the ball. A lot of the forward motion and followthrough happen after you hit the ball.

All are correct and great videos. I might be wrong, but it looks like you are serving with an eastern forehand grip. This allows limited movement of your wrist(so pronation is difficult) and hampers spin. Learn the continental grip or eastern backhand grip for serving and lower that toss to as gravity pauses the ball, and is just about to come down, you are making contact with the ball.